The present invention relates in general to the field of guidewires. Guidewires are used to position catheters in exploratory procedures, diagnosis, and treatment of various medical conditions. More particularly, this invention relates to a guidewire extension system for connecting or coupling a guidewire, primary or initial wire to an extension or secondary wire during a medical procedure.
Guidewires are used in various medical procedures to position medical devices at desired locations within a patient""s vascular system. Guidewires, which are steerable, are inserted and maneuvered through the patient""s vasculature to a previously chosen location. Once in place, the guidewire provides the means to place a non-steerable device, such as a catheter, at the chosen body site. For example, a catheter is slid over the guidewire until the catheter, or some working portion thereof, is positioned within the vasculature at the desired location. Generally speaking, guidewires of a standard length are longer than the non-steerable devices with which they are used to permit independent movement of the device and the wire.
Angioplasty is one surgical application where a guidewire is often used. In angioplasty a dilatation catheter having an inflatable balloon structure is used to compress occlusive or blockage material against the sides of a vessel, thereby permitting (ideally) circulation to be reestablished. In preparatory procedures, the site of a vascular restriction, occlusion or stenosis is identified. The guidewire is inserted into the patient""s femoral artery and maneuvered or steered to the location of the restriction. Insertion of the guidewire is facilitated by an video X-ray device which allows the surgeon to observe the movement of the guidewire""s distal tip. The guidewire distal tip generally comprises a radiopaque metal to enhance X-ray viewing. A dilatation catheter then is inserted over the guidewire so that its working segment is located adjacent the restriction. Generally this means that the catheter balloon is positioned adjacent the vascular restriction or blockage.
During a simple angioplasty procedure, the dilatation catheter balloon is inflated to open the restriction, and then is removed along with the guidewire. However, complications sometimes arise which prevent the surgeon from completing this simple procedure. Occasionally the balloon catheter malfunctions. Sometimes a larger (or smaller) balloon is required further to dilate the vascular restriction, or another device or other type of catheter is needed to remove vascular material. For whatever the reason, the guidewire extension system of this invention is used when the catheter, or other such device, has to be removed and replaced with another device or catheter.
In the usual procedure to exchange catheters, the guidewire is removed from the patient leaving the catheter in the vascular system. An exchange wire is inserted through the catheter and the catheter removed, leaving the exchange wire in place. . The new catheter is inserted over the exchange wire and the exchange wire removed and replaced with the guidewire.
It is desirable to keep the guidewire in the patient""s vasculative for various reasons. However, the primary reason for not removing the guidewire is that the initial placement of the guidewire requires extensive, time consuming, manipulation. Removal and repositioning of the guidewire would be equally time consuming, possibly requiring further exposure to drugs, exposure to additional radiation, and, in general, infliction of additional trauma to the patient.
In those cases where catheter exchange is desired, the surgeon could simply remove the catheter over the guidewire, leaving the guidewire in the patient. However, to facilitate the removal and replacement of a catheter, the guidewire must be sufficiently long to allow the surgeon to grip a portion of the wire as the catheter is being withdrawn. This requires the guidewire to be long enough to provide an external portion longer than the catheter in addition to the portion remaining in the patient.
Unfortunately, a guidewire of sufficient length has inferior handling characteristics, thereby making more difficult the steering and maneuvering manipulations needed for guidewire placement. The added length also imposes itself on the usually cramped surgical arena thereby causing distractions to other surgical support activities. It is for these reasons that guidewires are usually only slightly longer than balloon catheters, e.g. 20-50 centimeters longer, and that a much longer exchange wire (and exchange procedure) is used. In other words, the guide wire-extension wire combination has a length approximating that of an exchange wire. Illustrating the above, a dilatation catheter has a length in the range of about 130 cm to about 160 cm, a suitable guidewire would have a length in the range of about 160 cm to about 200 cm and an exchange wire would have a length in the range of about 260 cm to about 340 cm. As can be imagined from the above, utilization of an exchange wire in an exchange wire procedure is complicated and time consuming. This invention simplifies catheter exchange and eliminates the need to use an exchange wire.
A recent development involves coupling or connecting a second length of wire, sometimes called an extension wire or secondary wire, to the exposed, proximal end of a guidewire. The second wire length should be of sufficient length to allow the catheter to be withdrawn while leaving the guidewire in the patient. Various approaches have been suggested for effecting the attachment of an extension wire to a guidewire.
In one approach, such as that described in U.S. Pat. No. 4,922,923 to Gambale et al., a guide wire and an extension are joined together by crimping. A special crimping tool is disclosed in the Gambale et al., ""923 patent. A drawback of this approach is that once the wires have been crimped, the connection therebetween is substantially permanent, and the extension wire cannot be detached from the guidewire except by severing it, e.g., by cutting.
Instead of crimping the guidewire to the extension wire, attempts have been made to engage the extension wire to the guidewire frictionally. Such attempts are described, for example, in U.S. Pat. No. 5,113,872 to Jahrmarkt et al., and related U.S. Pat. No. 5,117,838 to Palmer et al. These two patents disclose a guidewire extension system in which the distal end of the extension wire comprises a small diameter tube in which there is disposed a small diameter, open pitch, flat wire coiled spring. The proximal end of the guidewire has a reduced diameter portion which is inserted into the tube assembly to complete the connection. The reduced diameter proximal end of the guidewire is slightly larger than the internal diameter of the coiled spring of the extension wire, thereby creating a frictional engagement when one is inserted into the other. Palmer et al. disclose the utilization a swivel joint for minimizing twisting of the extension guidewire when connecting or disconnecting it from the extension wire. A device as described in these two patents would be very difficult to manufacture reliably and apparently requires an alignment tool to ease insertion.
U.S. Pat. No. 4,875,489 to Messner et al., discloses an extendable guidewire in which concentric tubular segments are secured to one or the other of the sections to be connected. The inner tubular segment has a longitudinal slot therein which permits it to expand when a cooperating male portion is inserted therein. The outer tubular member of the connector assembly restricts the expansion of the inner tubular member as the male portion is inserted therein.
U.S. Pat. No. 4,846,193 to Tremulis et al., disclose a guidewire having first and second telescopically extendable sections movable between axially extended and retracted positions. No disengagement of the guidewire and extension wire is disclosed.
U.S. Pat. No. 4,966,136 to Kraus et al., discloses an internally threaded female connection member secured to the distal end of the extension wire. The internally threaded female connection member is disclosed to be freely rotatable with respect to the extension wire by securement thereto by means of a collar. The body of the extension wire has a distal enlargement which cooperates with the collar to permit it to be freely rotated. The female connection member of the extension wire cooperates with a threaded male portion located on the proximal end of the guidewire. The mechanism disclosed by Kraus et al., however, sacrifices pushability and flexibility as the ball and socket joint do not effect a mechanical lock sufficiently to transmit such desirable properties.
U.S. Pat. No. 4,827,941 to Taylor et al. discloses a guidewire extension system employing a tubular female connector portion on one wire and a cooperating male portion on the other. The connecting male portion has an effective diameter in one radial dimension which is slightly larger than the inner diameter of the tubular portion. In a preferred practice, the male end portion of the Taylor et al. guidewire has an undulating shape, which, when inserted into the tube creates an interference fit.
The guidewire extension systems discussed above all have drawbacks. Either they have not provided easy engagement or they have disengaged too easily. While frictional engagement overcomes the disadvantages of crimping, disengagement may occur. Problems of kinking at the connection have been experienced with some systems. Moreover, prior extendable wires for use in coronary angioplasty procedures have been found to be unsuitable in peripheral arteries because the connections are not strong enough. Further, some connections have larger diameters than the rest of the guidewire system. This may cause snagging of the catheter. It also means that the catheter with which such connection system is used must have a larger internal diameter than would be necessary were a smaller diameter coupler employed.
Accordingly, a principal object of the present invention is to provide a threaded-type guidewire extension system which is reliable, easy to use and easy to manufacture.
It is a further object of the present invention to provide a guidewire extension system which minimizes the possibility of system failure by kinking or undesirable bending at the connection between the guidewire and the extension wire.
Another object of the present invention is to provide a guidewire extension system utilizing what is referred to as a turnbuckle configuration which does not require that either the guidewire or extension wire be rotated when attaching one to the other. It is advantageous that the guidewire be held stationary because the guidewire is located within the patient""s blood vessel where. unnecessary movement can induce trauma. It is also advantageous to have the majority of the length of the extension wire held stationary during the connection process. Having the extension wire self-contained in its tubular carrier package allows medical personnel to concentrate upon engaging the two wires. An uncontained extension wire is awkward, and thus complicates the process of effecting a guidewire/extension wire union during a medical procedure.
It is still a further object of the present invention to provide a guidewire extension system which has substantially the same flexibility and pushability at its connection as that of the remainder of the length of the guidewire.
It is yet another object of the present invention to provide a unitized guidewire extension system having a uniform, smooth, continuous outer diameter along the guidewire, connector, and extension wire. Methods of manufacturing an extension system of this invention and methods of using a system of this invention also are disclosed.
Briefly, in one aspect, the present invention is an extension system for rotatively connecting the proximal end of a guidewire to the distal end of an extension wire. In accordance with the present invention, the system comprises engagement means, such as threads located on the proximal end, and distal end, respectively, of a guidewire and an extension wire. The system further includes a cylindrical sleeve, coupler, or connector, the connector having a deformable wall or body wall. The deformable body wall defines openings on each end of the connector and a cavity extending between the openings. The body wall further defines oppositely pitched, exteriorly-formed, interior threads. The oppositely-pitched, interior threads extend toward the center of the connector. In one embodiment, the interior threads run the entire length of the connector body and meet at approximately the middle. In a preferred practice, the externally-formed internal threads begin at a point interiorly disposed from the openings. This leaves a segment of the body wall which is substantially smooth between the sleeve openings and the start of the thread. The threads are adapted to cooperate with the respective engagement means of the guidewire and extension wire so that the engagement means are retained within the sleeve.
The system further comprises means for rotatively retaining the connector on one or the other of the guidewire or extension wire. In one embodiment, this retention means comprises an annular bead or dent in the sleeve. The annular bead is of sufficient width so that it will not pass over threads on the guidewire or extension wire on which it is located. Thus the guidewire and extension wire may be connected or coupled by inserting the engagement means into the connector and rotating the connector in a single direction.
In a method of making the present extension system, the externally-formed, internal thread is roll formed by rolling a deformable, suitably thin walled, sleeve material over an elongate protuberance, skin or projection from an otherwise substantially flat surface. The sleeve, which has an axis, is rolled over the projection at an angle with respect to its axis with sufficient force to deform the connector body create therein a substantially continuous, external bead or dent. The sleeve body is sufficiently thin so that rolling the sleeve body over the shim creates an internal, helical thread according to the invention. Having rolled the sleeve in one direction to create an internal thread of a first pitch, the process is repeated, starting adjacent the remaining end of the sleeve, to create the second oppositely pitched thread. In a further embodiment, the oppositely pitched threads could be created in a single step by rolling the deformable sleeve, with sufficient force, in one direction over two obliquely angled (i.e., defining an open xe2x80x9cVxe2x80x9d ), elongate shims.